[llvm] [AMDGPU] Use absolute relocations when compiling for AMDPAL and Mesa3D (PR #67791)

[Matt Arsenault via llvm-commits]

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@@ -2762,7 +2766,46 @@ bool AMDGPULegalizerInfo::buildPCRelGlobalAddress(Register DstReg, LLT PtrTy,
   if (PtrTy.getSizeInBits() == 32)
     B.buildExtract(DstReg, PCReg, 0);
   return true;
- }
+}
+
+// Emit a ABS32_LO / ABS32_HI relocation stub.
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arsenm wrote:

Why do this here instead of selection of the address? The G_GLOBAL_VALUE is more useful for post-legalize combines 

https://github.com/llvm/llvm-project/pull/67791